In recent years, in a computer system which deals with a large scale of data, data is stored in a large-capacity storage apparatus provided separately from a host computer.
In the case where a storage apparatus within a computer system which is required to operate 24 hours a day, every day is migrated to (replaced with) a new storage apparatus, it is desirable that I/O is not stopped; that is, data exchange between the host computer and the storage apparatus is not stopped.
Further, in migration of the storage apparatuses, it is desirable that an existing apparatus such as a host computer, a migration source storage apparatus and a network apparatus does not need to have a special function. For example, concerning migration of the storage apparatus, it is desirable that an alternate path program of the host computer is a program (function) provided by an operating system of the host computer, that a function of the migration source storage apparatus complies with SCSI (Small Computer System Interface) standards, and that a function of the network apparatus complies with FC (Fibre Channel) standards.
For example, PTL 1 discloses the following computer system. That is, the computer system includes a host computer, a first storage apparatus having a first storage device and a second storage apparatus having a second storage device. The first storage apparatus provides a storage area of the first storage device to the host computer as a first logical unit. The second storage apparatus virtualizes the first logical unit and provides the virtualized first logical unit to the host computer as a second logical unit, collects configuration information of the first logical unit and configures the collected configuration information at the corresponding second logical unit. The host computer adds a path to the second logical unit and deletes a path to the first logical unit. The second storage apparatus copies data stored in the first logical unit to a storage area provided by the second storage device and associates the storage area with the second logical unit.